1. Field of the Invention
The present invention relates to rotatable cutting tool assemblies and more specifically to rotatable cutting tool assemblies having sleeve retainers for removable attachment of the cutting tool within a bored tool holder.
2. Description of the Related Art
The present invention is directed toward a cutting tool assembly employed in earth working, mining or construction applications wherein a cutting bit is held on a mounting block or bit holder that is affixed to a movable member. Such cutting tool assemblies have been employed for various excavating operations. These excavating operations can include removal of minerals as well as trenching, concrete cutting, road planning and other construction applications. The cutting tools must be held securely in place and yet be free to rotate in order to promote uniform wear on the respective tip portions. While earlier cutting tool assemblies have preformed satisfactorily, certain problems or drawbacks have existed and the subject invention is directed toward overcoming these problems.
Cutting tool assemblies of the prior art often include cutting bits having shank portions with enlarged diameters or sharp, stepped or flanged portions at the rear of the shank. Examples of this type of cutting tool assembly can be found in U.S. Pat. No. 4,201,421 to Den Besten et al. as well as U.S. Pat. No. 4,684,176, also to Den Besten et al. However, the rear shoulder on the shank portion of the cutting bit adds cost to the overall tool assembly and, to that extent, is undesirable. Furthermore, the retaining sleeves which are commonly employed in cutting tool assemblies can become positioned between the enlarged shoulder or stepped diameter of the shanks of the cutting tools of the prior art and the cylindrical bore wall thus wedging the sleeve into the bore and making it difficult to extract the bit from the mounting block. In such cases, the block is usually removed and replaced thus adding to the expense of the excavating operation.
Prior art cutting tool assemblies have also employed cylindrical retainer bore clips which are disposed between the rear stop shoulder on the shank of a cutting bit and the rear face of the mounting block as shown, for example, in FIG. 10 of the '176 patent to Den Besten et al. Retainer clips of this type add cost to the cutting tool assembly and are generally more time consuming during installation and extraction of the cutting bit to the mounting block.
There is a need in the art for a cutting tool assembly wherein the cutting bit will be adequately retained within the mounting block without inadvertent removal of the cutting bit due to the forces acting thereon during excavating operations. Further, there is a need in the art for a cutting tool assembly which eliminates the requirements for rear stop shoulders on the shank of the cutting bit thereby reducing the machining requirements on the bit and otherwise simplifying the system and reducing costs.
The subject invention overcomes the problems in the prior art in a cutting tool assembly having a retainer scheme which effectively and rotatably retains the cutting bit within the mounting block while at the same time preventing inadvertent removal of the cutting bit during excavating operations.